Drainage management systems and methods

ABSTRACT

A flow limiting inlet structure is designed to collect water or other fluids in a pool above grade, and to provide improved capture of sediments and surface pollutants such as oils and greases in the pool, while regulating the flow of water or other fluids during discharge into an outlet pipe. In a conventional storm water detention basin a vertical cylindrical discharge structure can be used to regulate the basin water depth and discharge flow rate of storm water out of the detention basin, in conjunction with the use of a specially designed baffle system that prevents the release of any greases or oils floating on the water surface while capturing any floating trash or debris.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of pending U.S. application Ser. No.10/692,507, filed on Oct. 24, 2003, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The field of the invention is drainage management systems, moreparticularly, flow limiting inlet structures designed to collect wateror other fluids in a pool above grade and to regulate water discharge,enabling the system to capture sediments and surface pollutants such asoil and grease in the pool before allowing, the collected water todischarge into an outlet pipe.

BACKGROUND OF THE INVENTION

Contaminated sediments, greases, and oils, and other pollutants collecton the ground during dry periods when little or no rainfall occurs. Whena storm occurs after such a dry period, the accumulated pollutants aremobilized by storm water and get flushed into surface water drainagesystems. The flushing of pollutants into such drainage systems isgenerally undesirable, particularly if the water or other fluids flowingthrough such drainage systems remain untreated before being dischargedinto a river, lake, or ocean. The occurrence of a storm after a dryperiod and the corresponding flushing of pollutants into drainagesystems is often referred to as a “first flush” event. First flushevents are particularly troublesome in industrial areas due to the typesand amounts of pollutants that accumulate.

Because the effects of first flush events are undesirable, efforts havebeen made to limit such effects. A common way to do so is to allow stormwaters to initially flow into a detention basin and to use a flowlimiting stricture to control flow out of the detention basin. Such flowlimiting structures include, among others, risers, trash racks, filters,and weirs. Such structures typically try to allow sediments to settleout, prevent the outflow of surface contaminants, or prevent the outflowof larger sized pollutants.

A concern in designing such flow limiting structures is that they shouldnot allow flooding to occur, even if preventing flooding allowspollutants to escape. As a result, flow-limiting structures aretypically designed to provide for “overflow” situations during whichquantities of water in excess of the design first-flush storm areallowed to flow through the structure untreated if the incoming watervolume exceeds the capacity of the system. In an attempt to help preventoverflow from occurring, some structures such as perforated risers aredesigned to permit a higher flow rate through an outlet as water levelsrise.

Unfortunately, previously known flow-limiting structures do not alwaysprovide a solution that adequately balances the design goals ofpreventing flooding, allowing sediments to settle, preventing flushingof surface pollutants, and limiting peak discharge flow rates. As such,there is a need for new flow limiting structures such as are disclosedherein.

SUMMARY OF THE INVENTION

The present invention is directed to a flow limiting inlet structuredesigned to collect water or other fluids in a pool above grade, and toprovide improved capture of sediments and surface pollutants such asoils and greases in the pool, while regulating the flow of water orother fluids during discharge into an outlet pipe. More particularly,the present invention is directed to the use of a conventional stormwater detention basin, and the use of a vertical cylindrical dischargestructure to regulate the basin water depth and discharge flow rate ofstorm water out of the detention basin, in conjunction with a speciallydesigned baffle system that prevents the release of any greases or oilsfloating on the water surface while capturing ally floating trash ordebris.

If a perforated discharge structure is used, the location and diameterof holes in the discharge structure can be varied to produce a widevariety of discharge flow rates so as to control the approach velocityof incoming storm water and promote complete settlement of suspendedsediments. This system attenuates the peak storm water inflow rate andreduces the peak discharge flow rate as needed. Flow in excess of “firstflush” volumes pass through the system untreated by entering the top ofthe discharge structure while concurrently flowing over a basinperimeter weir set at the same elevation. These larger storm volumes arenot completely attenuated nor treated by the detention basin.

After a storm has passed, site staff can shovel out the collectedsediment from the detention basin, washout all of the accumulated greaseand oil, and in so doing make the system ready for the next storm event.

It is contemplated that the methods and systems disclosed herein areparticularly well adapted for use in managing the quality of stormwaters draining from industrial sites. However, it is also contemplatedthat the methods and systems disclosed herein will prove advantageous inother drainage and/or fluid control applications.

In one embodiment, the present invention comprises a storm waterdetention basin comprising a basin sized and positioned to accumulatestorm water, an outlet, and a flow limiting structure impeding flow ofwater out of the basin through the outlet, the flow limiting inletstructure comprising: a set of one or more baffles adapted to hinder theflow of surface contaminants into the outlet; and a discharge riseradapted to control the discharge flow rate out of the basin toeffectively capture sediment in the basin. In some such embodiments theset of one or more baffles are a tiered set of nested baffles whereineach baffle that is nested within another baffle is positioned at alower height than the baffle it is nested within, and the baffles of theset of baffles overlap each other. This nested set of baffles is designto prevent the release of a water surface containing floating oils andgreases, and has adequate nested baffle overlap to prevent the releaseof such oil and grease when the water surface is depressed passingthrough the baffle system.

In another embodiment the present invention comprises a flow limitinginlet structure comprising a set of one or more baffles adapted toinhibit the flow of surface materials through the baffle set, whereinthe inlet area of the baffle set increases as fluid depth increases.

In another embodiment, the present invention comprises a flow limitinginlet structure comprising a discharge riser surrounded by a tiered setof nested baffles. In some such embodiments, each baffle that is nestedwithin another baffle may be positioned at a lower height than thebaffle it is nested within, and the baffles of the set of baffles mayoverlap each other. Such a flow limiting inlet structure comprising adischarge riser surrounded by a tiered set of nested baffles may alsohave a lower inlet area of a baffle of the set of baffles that is lessthan the non-overflow inlet area of the discharge riser. In someinstances the difference may be great enough that the lower inlet areaof a baffle of the set of baffles is less than half or even less thanone third of the non-overflow inlet area of the discharge riser.

Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of a flow limiting input structure in adetention basin.

FIG. 1B is a side view of the flow limiting input structure of FIG. 1A.

FIG. 1C is a cutaway side view of the flow limiting input structure ofFIG. 1A.

FIG. 1D is a bottom view of the baffles and riser of the flow limitinginput structure of FIG. 1 a.

FIG. 2A is a partial cutaway side view of the flow limiting inputstructure of FIG. 1A illustrating operation of the structure at a firstfluid depth.

FIG. 2B is a partial cutaway side view of the flow limiting inputstructure of FIG. 1A illustrating operation of the structure at a secondfluid depth.

FIG. 2C is a partial cutaway side view of the flow limiting inputstructure of FIG. 1A illustrating operation of the structure at a thirdfluid depth.

FIG. 2D is a partial cutaway side view of the flow limiting inputstructure of FIG. 1A illustrating operation of the structure at a fourthfluid depth.

FIG. 3A is a cutaway side view of a second flow limiting inputstructure.

FIG. 3B is a bottom view of the flow limiting structure of FIG. 4A.

FIG. 4 is a bottom view of the baffles and riser of an alternativeembodiment of the flow limiting input structure of FIG. 1 a.

FIG. 5 is a partial cutaway view of an alternative baffle set.

FIG. 6A is a cutaway view of an alternative baffle.

FIG. 6B is a cutaway view of an alternative baffle.

FIG. 7 is a cutaway side view of the input structure of FIG. 1 providingreference numbers for various measurements.

DETAILED DESCRIPTION

In FIG. 1A, a flow limiting structure 100 is positioned in a detentionbasin 20 where basin 20 is partially bounded by basin bottom 21 and bybasin perimeter weir 22, and basin 20 includes an outlet 160. Basin 20contains sediment and surface pollutant containing water 10, andstructure 100 controls the flow of water 10 (or any other fluid in basin20) out of basin 20 through outlet 160. In preferred embodiments, weir22 is adapted to spill water out of basin 20 when water 10 reaches aheight sufficient to overflow stricture 100.

As can be seen in FIGS. 1A-1D, flow limiting structure 100 comprises aperforated riser 110 having holes 111 and opening 112 covered by hingedgrate 113, and a set of two nested and tiered baffles 120 and 130, eachbaffle (120, 130) comprising lower edges (121, 131) forging loweropenings (122, 132), upper edges (123, 133) forming upper openings (124,134), and a set of support legs (125, 135), separating lower edges (121,131), from a foundation 150. Baffles 120 and 130 are tiered in the sensethat the distance of separation between lower edges 121 and 131 differsbetween each of the baffles as do the heights of upper edges 123 and133. Baffle 120 is nested within baffles 130 in that baffle 130 at leastpartially surrounds baffle 120 and baffle 120 is positioned betweenbaffle 130 aid riser 110. Baffle 120, in turn, surrounds riser 110.Baffles 120 and 130 overlap in that upper edge 123 of baffle 120 ishigher than lower edge 131 of baffle 130, while lower edge 121 of baffle120 is lower than lower edge 131 of baffle 130. Structure 100 controlsfluid flow into outlet 160 and outlet pipe 170.

FIGS. 2A-2D illustrate the flow input structure 100 of FIGS. 1A-1D asthe structure operates to control flow of fluid 10 out of the basinthrough outlet 160. In FIG. 2A, fluid 10 has a depth D1 at which thesurface of fluid 10 is below lower edge 121 of baffle 120 and the lowestset of openings 111 in riser 110. As such, at depth D1 fluid 10 isprevented from flowing through outlet 160 by riser 110. In FIG. 2B,fluid 10 has risen to a level D2 above edge 121 and the lowermost set ofopenings 111. As such, fluid 10 is able to flow through flow paths Flunder baffle 120, into riser 110, and out outlet 160. In FIG. 2C, fluid10 has risen to a level D3 above lower edge 131 and above upper edge123. As such, fluid 10 is able to flow under baffles 120 and 130 andinto riser 110 through the four lowermost sets of holes 111 in riser 110via flow paths Fl-F4. In FIG. 2D, fluid 10 has risen to a level D4 aboveupper edge 131, but just below the upper edge of riser 110 that definesopening 112. As such, fluid 10 is able to flow both over and underbaffles 120 and 130 into riser 110 through all the sets of holes 111 inriser 110 via flow paths F1-F5.

It should be noted that flow paths F1-F5 are provided for illustrativepurposes only. The actual flow paths through the baffles and riser willlikely vary based on a number of factors such as the size, relativespacing, and positions of the holes, risers, and baffles as well as thenumber and shape of the baffles.

Many of the features of structure 110 are equally applicable toside-discharge structures as illustrated in FIGS. 3A and 3B as they areto bottom discharge structures as shown in FIGS. 1A-1D. In FIGS. 3A-3B,a flow limiting input structure 300 is used to control flow of fluidsthrough side outlet 310 where the structure comprises tiered and nestedbaffles 320, 330, 340, 350, 360, and 370. As shown in FIGS. 3A and 3B,flow limiting input structures as disclosed herein (whether for side orbottom discharge outlets) need not comprise any riser or other flowcontrol device other than the set of nested and tiered baffles. However,although the sizes, positions, and relative spacing of the baffles in abaffle set could be used to control flow rate of fluid into an outlet,it is preferred that a riser or other flow control apparatus be used inconjunction with the baffle set to provide simpler flow rate control,and to provide more options in regard to baffle design. In preferredembodiments, the baffles of a baffle set will be spaced sufficiently farfrom each other, from the discharge riser, and from the foundation thatflow rate through the outlet 160 is substantially, if not totally,determined by any discharge riser or other flow rate control apparatusused in conjunction with the baffle set.

If one compares structure 300 of FIGS. 3A-3B with structure 100 of FIGS.1A-1D, it is apparent that the number of baffles in the baffle set ofstructure 300 is greater than the number of baffles in the baffle set ofstructure 100. The number of baffles will vary between differentembodiments, but preferred embodiments will comprise at least twobaffles, while more preferred embodiments will comprise three or morebaffles. It is contemplated that increasing the number of baffles allowsfor reduced spacing between baffles and between the innermost baffle andany riser, with a corresponding decrease in surface contaminants thatmay make it into structures 100 and 300 as being on a surface of fluid10 inside the perimeter of a baffle as the fluid level rises from belowto above the lower edge of the baffle. As such, a design comprising asingle baffle sized large enough to allow for maximum flow thorough theoutlet may allow larger amounts of initial leakage of surfacecontaminants at low fluid levels and is the less preferred than designsthat utilize a larger number of baffles.

Such a comparison between structure 300 and structure 100 also makes itapparent that the shape of baffles differs between structure 100 andstructure 300. When viewed from the top or bottom, the shape of thebaffles of a particular embodiment may be square (see FIG. 1D), circular(see FIG. 4), semi-circular (see FIG. 3B), elliptical, or any othershape. Although the embodiments shown have baffle sets wherein everybaffle of the set has substantially the same shape as every otherbaffle, less preferred embodiments may have any combination of similarlyor differently shaped baffles within a baffle set. FIGS. 3A and 5illustrate that baffle shapes may vary in other ways as well. In FIG.3A, one baffle of the set forms a hood over the other baffles, while inFIG. 5 each baffle forms a partial hood that can help direct flow fromhigher baffles or from overflow into the structure. Moreover, bafflesneed not be elongated such that their height exceeds their width asshown in the pictured embodiments. As such, baffles may comprise anyshape so long as they function to minimize the amount of surfacecontaminants that flow through the flow limiting input structure theyare a part of.

Although the baffles shown in FIGS. 1A-1D comprise support legs (125,135), other embodiments may utilize different mechanisms for providingbaffle support. Any mechanism that supports the baffles while stillallowing them to function to prevent flow of a majority of surfacecontaminants through the inlet structure may be used. As an example,baffles may hang from a bracket or other structure that couples them toa discharge riser, or may all be coupled to one or more baffles thatprovide support to any other baffles. Another example can be seen inFIG. 3A where the baffles 320-370 may be coupled directly to the sidewall that outlet 310 pass through. Yet another option similar to the useof support legs is to use outer baffles that are self supporting buthave slots, perforations, or some other feature that permits water toflow through the lower portions of the baffles such as the baffles ofFIGS. 6A and 6B.

It is also contemplated that instead of using “short” baffles (i.e.baffles that don't extend to the top of the structure), one or more ofthe baffles, particularly the innermost baffle (120, 320) may beextended upwards but have the extended portion comprise perforations orslots, or otherwise be adapted to allow fluid to flow through suchextended portions. It is contemplated that the use of a partiallyperforated inner baffles would minimize or eliminate the need for anycentral discharge riser as the functionality of such a riser would beprovided by the upper portions of the interior baffles.

Gaps between baffles and any gap between the innermost baffle and ariser, may include strainers, filter, vanes, or other fluid controlmechanisms. It is contemplated that the use of filters in the gapsbetween baffles may prove advantageous as at least some materialscaptured in such filters may fall free once fluid levels drop below theheight of the filter. It also is contemplated that the use of vanes orother fluid control mechanisms may be advantageously used to improveflow through the flow limiting input structure. Some input structuresmay be designed to include such screens or filters and also tofacilitate the flushing of such screens of filter, possibly withoutrequiring fluid levels to drop below filter heights.

As illustrated by FIGS. 2A-2D, the number of flow paths through the setof baffles (120, 130) increases as the depth of fluid 10 increases. Theterm “flow path” is used herein to denote any path through which fluidcan flow for the current level of fluid. As such, there are no “flowpaths” through structure 100 in FIG. 2A as the riser prevents flow offluid 10 through the structure at a depth/head D1 (measured between thesurface and the top of base 150 which defines the top of outlet 160). Ata depth D2, structure 100 comprises flow paths F1 under baffle 120 andinto the lowermost set of holes 111. At depth D3, structure 100comprises additional flow paths F2-F4, and at depth D4 also includesflow path F5. The flow paths through the baffle set (120, 130) do notnecessarily increase at the same rate as the flow paths through riser110, or structure 100, as the flow paths through the baffle set dependon the number, size, and relative positions of the baffles in the set.In contrast, the number of flow paths through structure 100 depends onboth the number of flow paths through the baffle set and the number offlow paths through riser 110.

In conjunction with the increase in the number of flow paths, the totalinlet area of the baffle set (120, 130) and structure 100 increases asthe depth of fluid 10 increases. The term “total inlet area” is usedherein to denote the sum of the areas of the various openings betweenthe exterior and interior of structure 100 through which fluid can flowfor the current level of fluid. In the embodiment shown, this equates tothe sum of the areas of the various openings between the interior andexterior of the baffle set (120, 130) for non-overflow levels. At levelD1, the total inlet area is zero. At level D2, the total inlet area isequal to the area of opening 122, which is approximately equal to thearea defined by lower edge 121 minus the cross sectional area of riser110. At level D3, the total inlet area is equal to the area of opening122 plus the area of opening 113. At level D4, the total inlet area isequal to the area of openings 122, plus the area of opening 113, plusthe area of opening 134.

The actual sizes and positions of the baffles will vary betweenembodiments. However, referring to FIG. 7, in preferred embodimentsbaffles should overlap (i.e. B22<BH1) and should be nested (BR1<BR2)such that the higher baffles (130, 430-470) are outermost in order toprevent flow of surface contaminants out of the detention basin.Although many embodiments may have baffles of similar dimensions (suchas having B11 be approximately equal to B21), it is contemplated thatthe relative heights of the upper and lower edges of adjacent baffles ismuch more relevant to proper operation that the sizes of the bafflesused. In addition to being higher than the lower edges of outer baffles(BH1>B22), the top edges of inner baffles (120, 420-460) in preferredembodiments will be lower (BH1<BH2) than the top edges of outer baffles(130, 440-470) to provide additional access to the upper portions of anyriser. In preferred embodiments, the lower edges of outer baffles willbe higher than the lower edges of inner baffles (B22>B12) in order tospread flow paths across the length/height of the inlet structure ratherthan concentrating them at the bottom. Spreading the flow pathsdecreases that amount of fluid flowing into the structure near its baseand minimizes the amount of sediment pulled into the structure by suchbottom flows. Spreading flow paths along the structure also help toprevent the spacing between the bottoms of the baffles and thefoundation from becoming a limiting factor on the flow rate of thestructure. As sizes and positions may vary, different embodiments mayhave different values for B11, B12, B21, B22, BH1, BH2, BB, BR1, BR2,and R1-R6.

Riser 110 is preferred to be an elongated, perforated cylinder with avertical central axis, and may be tall enough to extend higher than thehighest baffle surrounding it. However, if it has an overflow inlet thatis positioned below the top edge of the outermost baffles, the bafflescan still act to prevent flow of surface contaminants into riser 110 andorifice 160 even when fluid levels are sufficiently great as to causeoverflow of riser 110.

In less preferred embodiments, riser 110 may not be perforated, may besubstantially shorter than the baffles surrounding it, or may beeliminated altogether. In less preferred embodiments, the orifices ofriser 110 may be positioned above the highest surrounding baffle ifsurface filtering of contaminants is less desired at higher fluidlevels. Similarly, riser 110 may permit fluid that flows under all thebaffles of the baffle set to flow into outlet 160 if surface filteringof contaminants is less desired at lower fluid levels. Although acylindrical shape is preferred, any riser used may be elliptical,polygonal, irregular or have some other shape. Although holes providingpassage from the exterior to the interior of riser 110 are preferred,other embodiments may use slits, rectangular orifices, filteredopenings, or some other mechanism to control the flow of fluid from theexterior of riser 110 to its interior. Riser 110 may, in someembodiments, be replaced with some other type of flow control apparatus.

In preferred embodiments the size and positions of the holes (or otherinlets) into riser 110 will be sufficient to allow as much fluid to flowinto riser 110 as can flow through outlet 160 such that overflow flowsthrough the top of the riser don't increase the throughput of the riserunless fluid is prevented from flowing into one or more of the holes inthe riser. Similarly, the baffles of the baffle set at least partiallysurrounding the riser and/or outlet will be sized and positioned suchthat the maximum amount of fluid that can be handled by the riser and/oroutlet flows through the baffle set without having to overflow thebaffle set.

In preferred embodiments the baffles and riser will comprise an open topto handle overflow conditions that may arise from large quantities offluid accumulating in the detention basin whether from a large storm,clogged inlets in the input structure, or some other reason.

However, less preferred embodiments may have riser and/or one or morebaffles that are closed on top.

In the embodiment shown, riser 110 comprises a hinged grate 113 thathelps prevent objects from flowing into riser 110 during overflowconditions. However, other embodiments may not have any similar type ofmechanism, or may use a mechanism other than a hinged grate. In someembodiments, a grate or similar mechanism may be used to filter baffleoverflows as well with such grates being used in conjunction with or inplace of grate 113.

It is contemplated that the various components of flow limiting inletstructures as disclosed herein may comprise different materials orcombinations of materials. The actual choice of materials will likely bedetermined based on the conditions a structure is expected to have toendure, and the desired life of the structure. In preferred embodiments,flow limiting inlet structures will be constructed of durable and Wresistant materials.

Thus, specific embodiments and applications of storm water controlbasins and flow limiting inlet structures have been disclosed. It shouldbe apparent, however, to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. As an example, althoughparticularly well adapted for storm water control, the apparatusdisclosed herein can be applied equally well to other fluid controlapplications where settling of sediment and/or filter of surfacematerials is desired. As an example, fluid accumulating in a detentionbasin may be the result of a container being drained or a surface beingwashed rather than a storm. The inventive subject matter, therefore, isnot to be restricted except in the spirit of the appended claims.Moreover, in interpreting both the specification and the claims, allterms should be interpreted in the broadest possible manner consistentwith the context. In particular, the terms “comprises” and “comprising”should be interpreted as referring to elements, components, or steps ina non-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.

1. A storm water detention system comprising: a basin sized andpositioned to accumulate storm water, an outlet, and a flow limitingstructure impeding flow of water out of the basin through the outlet,the flow limiting inlet structure comprising: a tiered set of bafflesadapted to hinder floating surface contaminants into the outlet; adischarge riser having openings such that the openings are sufficient toallow as much fluid to flow into the riser as can flow through theoutlet; wherein each of the baffles has a upper edge and a lower edge;the upper edge defines a upper opening; the lower edge defines a loweropening a filter located between the upper edge of a baffle and thelower edge of another of the tiered set of baffles; and wherein eachbaffle is coupled to the riser such that water is able to flow over theupper edge into the openings of the discharge.
 2. The system of claim 1wherein the set of baffles are a tiered set of nested baffles wherein:each baffle that is nested within another baffle is positioned at alower height that the baffle it is nested within; the baffles of the setof baffles overlap each other; the difference in height between theupper edge of any baffle that is nested within another baffle and thelower edge of the baffle it is nested within is at least ½ inch; andwherein the baffles have relative spacing such that openings in therisers are sufficient to allow as much fluid to flow into the riser ascan flow through the outlet.
 3. The structure of claim 1 wherein a lowerinlet area of a baffle of the set of baffles is less than annon-overflow inlet area of the discharge riser.
 4. The structure ofclaim 1 wherein a lower inlet area of a baffle of the set of baffles isless than half an non-overflow inlet area of the discharge riser.
 5. Thestructure of claim 1 wherein a lower inlet area of a baffle of the setof baffles is less than one third an non-overflow inlet area of thedischarge riser.
 6. A flow limiting inlet structure for use with a stormwater detention basin comprising a discharge riser surrounded by atiered set of nested baffles wherein an inlet area of the set increasesas fluid depth increases, and at least one baffle having a upper edgedefining a upper opening allowing water to flow through and furtherwherein each baffle is sized or configured such that openings in therisers are sufficient to allow as much fluid to flow into the riser ascan flow through an outlet of the storm water detention basin.